any ideas?

hi, I had the same problem with you. I tried to solve the problem with "setupInputMixer" example from Minim library, but I couldn't figure out. For an alternative way getting multiple audio data from my audio interface, I used Max/Msp or pure data with OSC. If you just want to get the amplitude, it will probably work without latency. Sorry for not a perfect answer.  

thanks, i've starte assuming it's not possible in minim. i am currently working on a solution using C# and NAudio